Flexible drill pipe



July 18, 1950 J. A. ZUBLlN FLEXIBLE DRILL PIPE Filed March 51, 1947 L M M A Patented July 18, 1950 fifth to Edward Adolphus Zublin, one-fifth to Casper Leonid Zublin, both of Los Angeles,

Calif.,

and one-fifth to Sonia Lynn-Thomas, New York, N. Y.

( Catherine) Application March 31, 1947, Serial No. 738,335 1 The'present invention relates to a novel form of flexible drill pipe.

Flexible drill pipe is employed in the drilling of bores deviating from existing well bores, more particularly in accordance with the method of my United States Patent 2,382,933. Heretofore, the resilient flexible metal drill guide has been constructed by slotting a straightdrill pipe along a line following a spiral which'runs with the desired pitch around the length-of the pipe section. Unslotted end portions are left for threading and to provide appropriate means for connecting the drill guide or stem into the drill string. Such a form of flexible drill guide is disclosed in my prior Patents 2,336,338 and 2,344,277.

The present invention contemplates an improvement upona flexible drill pipe structure and has as its specific object to provide a flexible drill pipe structure that is not subject to destruction or unwanted deformation in use,

Many oil wells are now'drilled to depths deeper than 4000 feet and, therefore, there is often considerable variation in the applicationv of weight as well as tension on a spirally slotted flexible drill pipe located in juxtaposition to the bit at the bottom of the well.

Experience has shown that a helically slotted flexible drill pipe with a smooth walled slot following a spiral around the length of the pipe will often become distorted when excess weight is imposed on the drill stem, either occasioned because of inaccuracy of the weight indicating. instrumentalities at the surface of the well or through unintentional carelessness of the driller. The application of excess weight' to the flexible drill stem having the smooth walled "spiral slot therein results in the distortion of the flexible pipe occasioning expansion of the helices thereof. Furthermore, the application of excess'tension sometimes permits the flexible drill pipe to be stretched out of shape, defeating itsintended purposes. I

It is, therefore, the'g'e'neral purpose and object of the present invention to provide a flexible drill pipe so slotted and constructed that the pipe retains the desirable flexibility and resiliency to bend along its longitudinal axis, but which is resistant to deformation under compression, torque, and preferably also under tension.

The objects of the present invention are obtained through the provision of an appropriately formed slot which extends spirally around the drill pipe. The details of the invention will become apparent as the description proceeds, which will be given by reference to the accompanying drawings which form a part hereof and in which:

'1' Claim. (01. 255-28) Figure 1 is a side elevational view "of a portion of a section of a flexible drill pipe conforming to the present invention; "i 1 Fig. 2 is a section on the line.2-2 of Figure 1, with diagrammatic representation of the forces which tend to effect distortion of the flexible drill stem; e i= Fig, 3 illustrates the-positioning of thewdrill stem of the present invention in anoil well where it is employed to drill a deviating bore.

In Figure 1, there is superimposed on-the drill pipe 1 6 a force diagram which maybe referred to to explain what normally happensto a spirally slotted drill pipe when excessive pressure is ap-' plied thereto. The compressiveforce indicated by the vertical arrow P1 in the force diagram of Figure I, normally exerts itself against-a smooth surface of a spiral slot, such as shown in Fig. 901 my prior Patent 2,336,338. This compressive force is divided into the component force P2 inthe direction of the arrow so designatedin the; force diagram of Figure 1, and the component force P3 designated by the arrow thus marked inthe:for ce diagram of Figure 1. It willbe observed that the component force P2 is atkright angles. to the normal helical slot whereas the component force P3 is parallel to the helical slot. When excessive weight isapplied to a drill stem such as [6, this weight creates pressure contact between theelas-v tic sections of the flexible drill stem above and below the helical slot. Therefore, if the excessive weight is represented by the pressure P1 which is applied equally and symmetrically aroundthe contour of the drill pipe, an equal number of component forces P2 andPa become effective along the spiral, forminga smooth-line of contact between the flexible sections ofthe drill stem above and below the'slot. By reference to Fig. 2'it will be clearly :seen how the component forces P3 arrange themselves tangentially around the circumference of the "pipe along the slot. These component forces P3 together form a powerful leverage which tends to open the drill pipe along the helical slot and to increase its diameter. If excess pressure in an amount suflicient to open the flexible drill pipe is imposed thereon, the upper section of the flexible drill pipe will telescope over the next lower section causing destruction of the unit of the flexible drill pipe. Even a lesser expansion than effective to cause telescoping of the section will nevertheless in some instances destroy the unit because the metal is pulled away from the high pressure rubber lining, indicated at 15 of Fig. 2, of the flexible drill pipe. The high pressure rubber lining of the flexible drill pipe, it will be appreciated, is unable to follow the excessive expansion in diameter of any given portion of the helically slotted drill pipe and thus becomes deprived of its metal backing, rendering it likely to burst under the inside fluid pressure of thehydraulicfluid employed to drive the bit atithe lower end Ofthe drill stem.

The disadvantages just described are those which have attended the use of the flexible drill pipe having a smooth walled spiral slot. As heretofore indicated, it is a specific purpose of-the present invention to so slot the flexible drill pipe that the portion thereof above the slot at any given point cannot move circumferentially in relation to the section'below the slot at that point thus facilitating rotation of the flexible drill pipe either in .a curved bore or a straight bore.

Specifically, it has been found that'a-spiral slot so cut in the wall of the drill pipe [6 as to provide intermeshing teeth above and below the slot zefiectivelyrsolves the difficult problem presented.

Anenibodiment "of theinvention is shown in Figure 11, wherein the metal -'dri1l pipe I6 is provided WiththBTSt 1.1 so cut through the vwall of the drill pipe I6 as to form the locking dovetail'itype teeth 'l8 -and'l9. It will be appreciated that the-slot fl 1 extends generally. along the path of the spiral lineifll. Whenemploying a flexible drill pipe conforming to the embodiment of Fig. 1, the spirally extendingslot of dove-tail pattern H will permit the necessary bending along the longitudinal axis of 'thefiexible drill pipe T6 to permit the same to effectively function in the drilling of deviating bores. The dove-tail teeth 18 and I 9 will, i however, effectively interlock the sections of the drill stem l6 above and below the slot-and prevent any 'movement'of these sections in respect to each other beyond the amount of movement -allowed by the width of the slot. These slots are adapted to be cut'by gas torch and their dimensions can be closely controlled and held -'-within prescribed limits. A pattern yielding intermeshing dove-tail teeth, such as teeth-[ 8 and IQ of Fig.1, can be readily cut and. accurately follow a spiral or any desired pitch along'the metal pipe. This may be accomplished through the employment of either an automatic or-non-automatic torch, both of'which arereadily availableon the market.

It will be appreciated that the width of the slot I! will determine the amount'of relative movement between the opposite dove-tailedteeth l8 and +9 of'the pattern and, therefore,'the width of the 'slot functions to regulate the over-all flexibility-orthe slotted pipe.

"In practical tests, it has been found thata slot varying from a of an inch to of an inch in width and having a pitch of the spiral --of about nine (9) inches for a four and 4 one-half (4 inch diameter drill pipe of hardened steel will yield a flexible resilient drill stem having the capacity to bend into a curve of an eighteen 8) foot radius, while at the same time providing a drill pipe having a compressive strength three (3) times greater and a tensile strength some ten (10) times greater than a comparable drill pipe provided with an ordinary smooth walled spiral slot.

vFrom the foregoing description it will be appreciatedthat, in accordance with the present inventionythere is;provided a flexible drill pipe adapted tobe employed as a drill guide in the drilling of deviating bores which will be safeguarded against distortion and destruction in use.

Having-thus described my invention, I claim:

An elongated, resilient, flexible, metal drill pipe comprising a tubular metal pipe having a slot of appreciable and uniform width through its wall extending in a generally helical path around and along the pipe, said slot deviating from a true :helical path to provide along the sides of the :slot. intermeshing and loosely interlocking teethzof dovetail configuration, each of said teeth having straight flat side edges which diverge from the root of the tooth to terminate in a straight flat 'end edge which is substantially parallel to the generally helical path of said slot,

the edges of said teeth being spaced from adjacent teeth by "the normal width of the slot While the pipe is in unstressed condition, and theedges of saidteethengaging adjacent teeth tolimit the extent of resilient deformation of said pipe upon application of tensile, compressive or torsion stressed to saidpipe.

JOHN A. ZUBLIN.

REFERENCES CITED .Thefollowing references "are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 218,744 House Aug. 19, 1879 369,865 Mann Sept. 13, 1887 556,819 Hartman Mar. 24, 1896 578,801 Wilmot Mar. 16, 1897 829,977 Lockwood Sept. 4, 1906 861,659 Johnston July 30, 1907 1,314,601 McCaskey Sept. 2, 1919 1,930,191 Bundy Oct. 10, 1933 1,943,035 Naylor Jan. 9, 1934 22963161 ,Hal1, Jr. Sept. 15,1942

2,336,338 Zublin Dec. 7, 1943 2,354,485 Slaughter July 25, 1944 2,362,817 Haycock Nov. 14, 1944 FOREIGN PATENTS Number Country Date GreatBritain Oct. 13, 1927 

